<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
    * {
        margin: 0;
        padding: 0;
    }
    ul{
        list-style: none;
        height: 226px;
        width: 609px;
        padding-top: 3px;
        padding-left: 3px;
        background-color: #ccc;
    }
    ul li{
        float: left;
        height: 40px;
        width: 100px;
        margin-right: 2px;
        margin-bottom: 2px;
        background-color: skyblue;
    }
    .float_right{
        float: right;
    }
    </style>
</head>
<body>
    <ul>
        <li>1</li>
        <li class="float_right">2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li class="float_right">6</li>
        <li>7</li>
        <li>8</li>
        <li class="float_right">9</li>
        <li>10</li>
        <li class="float_right">11</li>
        <li>12</li>
    </ul>
</body>
</html>